Phoma Destructiva Causing Blight of Tomato Plants: a New Fungal Threat for Tomato Plantations in Brazil?
Total Page：16
File Type：pdf, Size：1020Kb
Trop. plant pathol. (2018) 43:257–262 https://doi.org/10.1007/s40858-017-0200-2 SHORT COMMUNICATION Phoma destructiva causing blight of tomato plants: a new fungal threat for tomato plantations in Brazil? Adans A. Colmán1 & Janaina L. Alves1 & Meiriele da Silva1 & Robert W. Barreto1 Received: 17 July 2017 /Accepted: 24 October 2017 /Published online: 20 November 2017 # Sociedade Brasileira de Fitopatologia 2017 Abstract Solanum lycopersicum is among the most impor- Solanum lycopersicum (Solanaceae) is one of the most impor- tant crops in Brazil. This crop is affected by a large range of tant and broadly grown vegetables in the world. Brazil is fungal diseases that are recognized as major limitations for among the major producers of tomato worldwide (Vale et al. tomato production. Recently, plants grown in a greenhouse 2007). A large range of fungal and oomycete diseases affect in Viçosa, Minas Gerais, Brazil, were found to bear severe tomato (Jones et al. 2014; Lopes and Ávila 2005), some of blight symptoms. A pycnidial coelomycete was repeatedly which are universally regarded as major threats to tomato found in association with necrotic tissues. The fungus had its production, such as early blight, caused by Alternaria spp., morphology recognized as equivalent to that of Phoma and and late blight, caused by Phytophthora infestans. Others, related genera. A phylogenetic analysis based on nrDNA such as Phoma rot, are considered as having less relevance. (ITS) and partial β-tubulin (TUB) sequences led to the con- In Brazil, this disease is considered to be of secondary impor- clusion that the fungus involved was Phoma destructiva. tance (Inouie-Nagata et al. 2016). Although better known for Pathogenicity tests showed that, after 5 days, blight symptoms causing post-harvest disease of tomato fruits, Phoma developed on leaves, flowers and stems of plants belonging to (Didymellaceae) occasionally also affects stems and leaves thirteen different tomato varieties tested. This fungal species is in the field (Kimati et al. 2005;Robletal.2014). mostly known for causing post-harvest tomato rot, which is In July of 2015 several plants grown in a greenhouse in only regarded as a secondary disease in Brazil. This is in the campus of the Universidade Federal de Viçosa (Viçosa, disagreement with the observations made in this work. Here, state of Minas Gerais, Brazil), were found to bear severe the disease symptoms caused by the fungus were very severe, leaf blight symptoms (Figs. 1a, b). Lesions also appeared fully justifying the scientific name of the pathogen. Under on stems, which were similar to those seen on leaves favorable environmental conditions, aggressive strains of (Fig. 1c). All diseased plants died because of the disease. P. destructiva, such as the one isolated in this study, may A coelomycete asexual morph was repeatedly found in become significant threats to tomato plantations in Brazil. association with the necrotic tissues. Direct isolation of the fungus in pure culture was performed through aseptic transfer of spores from colonized tissue onto Keywords Solanum lycopersicum . Coelomycetes . PDA medium with a sterile fine-pointed needle. A representa- Didymellaceae . Pycnidial fungi . Phylogeny . Solanaceae tive isolate was deposited in the culture collection of the Universidade Federal de Viçosa, (Accession number COAD 2069). A representative dried specimen of infected tomato tis- sue was deposited in the herbarium of the Universidade Section Editor: Trazilbo J. Paula Jr. Federal de Vicosa (VIC 44080). Sections of selected fragments of infected leaves bearing fruiting bodies were mounted in * Robert W. Barreto [email protected] lactoglycerol for observation under a light microscope (Olympus BX 51) fitted with an Olympus e-volt 330 digital 1 Departamento de Fitopatologia, Universidade Federal de Viçosa, camera. Biometric data were recorded based on at least 30 Minas Gerais, Viçosa, MG 36570-900, Brazil measurements of various structures. 258 Trop. plant pathol. (2018) 43:257–262 Fig. 1 Phoma destructiva. a. Early stages of infection of Phoma destructiva on a tomato leaf. b. Ibid on flowers. c. Necrotic spots on stem and on a young sprout. d. Tomato plant with severe blight 20 days after inoculation. e. Transversal section of a pycnidium showing a layer of conidiogenous cells. f. Conidia with and without septa. Bars:e=8µmandf=20µm In order to obtain representative fungal DNA, COAD 2069 Purification Kit (Promega) following the protocol described was grown on PDA at 25 °C under a 12-h daily light regime by Pinho et al. (2012). for one week. DNA was extracted from approximately 40 mg The nrDNA (ITS) and partial β-tubulin (TUB) se- of fungal mycelium using the Wizard Genomic DNA quences of COAD 2069 were amplified using the primer Trop. plant pathol. (2018) 43:257–262 259 pairs ITS1/ITS4 (White et al. 1990) and T1/Bt2b, (Glass Table 1 GenBank accession numbers of Phoma spp. DNA sequences and Donaldson 1995;O’Donnell and Cigelnik 1997), fol- used in the phylogenetic analysis lowing the protocols described by Pinho et al. (2012)and Fungal species Strain number GenBank Acc. No. Sung et al. (2007). Amplification of ITS and β-tubulin, produced sequences of approximately 540 and 567 bp, re- ITS TUB spectively. The nucleotide sequences were edited with the Stagonosporopsis actaeae CBS 106.96 GU237733 GU237670 DNA Dragon software (Hepperle 2011) and deposited in CBS 105.97 GU237734 GU237671 GenBank under accession numbers MF 426960 for ITS P. acetosellae CBS 179.97 GU237793 GU237575 and MF448543 for β-tubulin. Additional ITS and β- P. aliena CBS 379.93 GU237851 GU237578 tubulin sequences used in this study were retrieved from CBS877.97 GU237910 GU237579 GenBank (Table 1). P. digitalis CBS 109.179 GU237744 GU237604 ITS and TUB consensus sequences were compared with CBS 229.79 GU237802 GU237605 others deposited in the GenBank database using the P. destructiva var. destructiva CBS 133.93 GU237779 GU237602 MegaBLAST program. The most similar sequences were CBS 378.73 GU237849 GU237601 aligned using MUSCLE (Edgar 2004) and built in MEGA P. destructiva TS24 KR559677 KU507405 v.5 (Tamura et al. 2011). All of the ambiguously aligned regions within the dataset were excluded from the analy- P. destructiva ICMP 14884 KT309887 KT309473 ses. Gaps (insertions/deletions) were treated as missing da- P. destructiva var. CBS 162.78 GU237788 GU237600 diversispora ta. Bayesian inference (BI) analyses employing a Markov P. bulgarica CBS 357.84 GU237837 GU237589 Chain Monte Carlo method were performed with all se- CBS 124.51 GU237768 GU237590 quences, first with each gene separately and then with the P. cr ys ta ll if er a CBS 193.82 GU237797 GU237598 β concatenated sequences (ITS and -tubulin). P. eu py re na CBS 374.91 FJ426999 FJ427110 Before launching the BI, the best nucleotide substitu- CBS 527.66 FJ427000 FJ427111 tion models were determined for each gene with P. herbarum CBS 615.75 GU237874 GU237613 MrMODELTEST 2.3 (Posada and Buckley 2004). Once CBS 502.91 FJ427022 FJ427133 the likelihood scores were calculated, the models were P. matteuciicola CBS 259.92 GU237812 GU237627 selected according to the Akaike Information Criterion P. omnivirens CBS 991.95 FJ427043 FJ427153 (AIC). The SYM + I + G model of evolution was used CBS 654.77 FJ427044 FJ427154 for ITS, whereas GTR + I + G was used for β-tubulin. P. polemonii CBS 109.18 GU237746 GU237648 The phylogenetic analysis of the concatenated sequences P. saxea CBS 419.92 GU237860 GU237655 was performed on the CIPRES web portal (Miller et al. CBS 298.89 GU237824 GU237654 2010) using MrBayes v.3.1.1 (Ronquist and Heulsenbeck P. insulana CBS 252.92 GU237810 GU237618 2003). The other phylogenetic analyses were conducted as described by Pinho et al. (2012). Sequences derived from P. multirostrata CBS 110.79 FJ427030 FJ427140 this study were deposited in GenBank (http://www.ncbi. CBS 274.60 FJ427031 FJ427141 nlm.nih.gov/genbank)(Table1), and the alignments and CBS 368.65 FJ427033 FJ427143 trees in TreeBASE (www.treebase.org) under entry P. pereupyrena CBS 267.92 GU237814 GU237643 number S21657. P. commelinicicola CBS 100.40 GU237712 GU237593 A pathogenicity test was conducted including thirteen P. costarricensis CBS 506.91 GU237876 GU237596 tomato varieties, namely: Forty, Ikram, Paronset, Platinum, CBS 497.91 GU237870 GU237597 Fusion, Santa Clara Siluet, Aguamiel, Caribe, Serato, Predador, Gladiador, Dominador and Vento. All varieties carry the Mi allele that confers resistance to root knot nem- atode (Meloidogyne spp.). COAD 2069 was grown on Phoma destructiva var. destructiva Plowr., Gard. Chron. II PDA medium at 25 °C for 7 days under a 12-h daily light 16: 621. 1881. regime and a conidial suspension (1 × 106 conidia/mL) was Disease: On leaves, stems and flowers, starting as small prepared for inoculation. Plants were sprayed with this black dots (1 to 2 mm diameter) that became circular to some- suspension until runoff and kept for 2 days in a dew cham- what irregular, slightly depressing the plant tissues and ber at 25 ± 3 °C and later transferred to a greenhouse. In forming zonate necrotic areas, where numerous fruiting bod- addition, two plants were sprayed with sterile water and ies were formed. Lesions coalesced with age and led to entire kept under the same conditions to serve as controls. blight of leaves, flowers and stems. 260 Trop. plant pathol. (2018) 43:257–262 Morphology: Internal mycelium indistinct; external myce- Based on morphology, P. destructiva has been separated lium absent; pycnidia immersed globose to irregular, 60– into two varieties P. destructiva var. destructiva and 150 × 70–180 μm, walls of thick textura angularis, ostiolate, P. destructiva var. diversispora differing in conidial size and brown, smooth; conidiogenous cells enteroblastic, septation (De Gruyter et al. 2002). Phoma destructiva var. ampulliform to doliiform, 4–6 × 3.5–8, hyaline, smooth; co- destructiva is aseptate and has been reported as a common nidia oval to ellipsoidal, 4.5–8 × 2.5–3 μm, mainly aseptate tomato and sweet pepper pathogen, causing fruit rot and small but larger 1-septate consistently produced, biguttulate, hya- black spots on leaves and fruits in the tropics.